1. Field of the Invention
The invention relates to vacuum insulating glazing consisting of two sheets of glass held apart by spacers and a peripheral seal.
The invention also relates to a process for producing such vacuum insulating glazing.
2. Discussion of the Background
To obtain thermal and/or acoustic insulation, it is usual to produce insulating glazing comprising two sheets of glass separated from each other by a relatively trick layer of air. Such glazing provides thermal insulation regarded as being insufficient for some applications. To remedy this, it is known to produce glazing which comprises three sheets of glass and one of the air layers may be replaced with a gas, for example krypton. Such glazing has markedly improved thermal insulation properties but its thickness is such that it is not always easy to use.
Moreover, the current demand by users is to move towards glazing thermal insulation equivalent to that of solid partitions, that is to say walls.
Insulating glazing has already been proposed, for instance in patent WO 91/02878, which consists of two sheets of glass separated from each other by a space in which a vacuum has been created.
Because of the vacuum, such glazing provides very good insulation, but it is very difficult to produce. Firstly, the small thickness between the two sheets of glass, which is a few tenths of a millimeter, must be constant over the entire area where the sheets of glass face each other. Secondly, the two sheets of glass must be sealed so as to be perfectly tight.
Patent WO 91/02878 describes a technique consisting in placing mounts a few tenths of a millimeter in thickness on one of the sheets of glass, distributed over the entire surface, and at the same time a seal which will allow the two sheets to be sealed. These studs and this seal are produced from the same material, which is a glass composition. It will be apparent that this glazing is difficult to produce because of these simultaneous steps which require tricky operations.
Patent Application FOR 96/09632 describes a process for creating a vacuum between two sheets of glass which may form insulating glazing. According to that process, the spacers are adhesively bonded by successively depositing amounts of an inorganic bonding compound, for example by screen printing, followed by spacers using a suction tool pierced with holes, smaller than the said spacers, with the same pitch as the mounts obtained. The spacers according to that process have a bitruncated spherical shape with parallel faces. Such a process requires a complicated apparatus and high precision in the operations.
The objective of the invention is to provide a process, which is simple to carry out, for producing vacuum insulating glazing, and the glazing produced.
This objective is achieved according to the invention by a process for producing vacuum insulating glazing, consisting of two sheets of glass held apart by spacers and a peripheral seal, which process consists, after the spacers have been deposited between the two sheets of glass, in sealing around the periphery and in creating a vacuum. The said process is such that spots of adhesive with a diameter less than or equal to the diameter of the spacers are deposited on one of the sheets of glass, the spacers are made to roll over the said sheet of glass so that only a single spacer adheres to each spot of adhesive and the second sheet of glass is deposited on the spacers and the peripheral seal.
According to a preferred embodiment of the invention, spherical spacers are made to roll. In this way, the shape of the spacer does not impose conditions on the deposition itself.
According to one advantageous embodiment of the invention, the sheet of glass is inclined by at least 1xc2x0 during the step of depositing the spacers. Thus, the inclination allows the spacers to encounter the spots of adhesive and also allows the spacers to be removed from the sheet by rolling when they have not encountered a spot of adhesive.
According to a preferred embodiment of the invention, the spots of adhesive are deposited by screen printing.
Advantageously, the spots of adhesive are spots of enamel.
According to a preferred embodiment of the invention, the spacers are compressed slightly during the phase of creating the vacuum.
The invention also provides vacuum insulating glazing that can especially be produced using the process described above.
According to the invention, the vacuum insulating glazing consists of two glass sheets held apart by spacers and a peripheral seal, the said spacers being metal balls bonded to only one sheet of glass by means of spots of adhesive and the said spots of adhesive having a diameter less than or equal to the diameter of the spacers so as to bond only a single spacer each time.
According to a preferred embodiment of the invention, the spacers have a diameter d1 of between 0.2 and 0.6 mm and the diameter d2 of the spots of adhesive is equal to (d1 xe2x88x920.1 mm)).
According to one advantageous embodiment of the invention, the spacers are slightly compressed between the two sheets of glass so as to have distributed contact areas matching the deformation of the glass.
Preferably, the adhesive is an inorganic compound and advantageously an enamel with a medium hardening by drying or curing.
According to a preferred embodiment of the invention, the metal spacer has a Young""s modulus less than or equal to 250 GPa and a yield stress less than or equal to 520 Mpa.
According to an advantageous embodiment of the invention, the spacer is made of stainless steel.